Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session T38: Focus Session: Quantum Coherence in Biology IV |
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Sponsoring Units: DCP DBP Chair: Mohan Sarovar, University of California, Berkeley Room: A130/131 |
Wednesday, March 23, 2011 2:30PM - 3:06PM |
T38.00001: Biophysics of Magnetic Orientation: Radical Pairs, Biogenic Magnetite, or both? Invited Speaker: Two major biophysical mechanisms for magnetoreception in terrestrial animals, one based on biogenic magnetite and another on radical-pair biochemical reactions, have been the subject of experiment and debate for the past 30 years. The magnetite hypothesis has stood the test of time: biogenic magnetite is synthesized biochemically in Bacteria, Protists, and numerous Animal phyla, as well as in some plants. Chains of single-domain crystals have been detected by clean-lab based SQUID magnetometry in animal tissues in all major phyla, followed by high-resolution TEM in selected model organisms, as well as by electrophysiological studies demonstrating the role of the ophthalmic branch of the trigeminal nerve in the magnetoreceptive process. Pulse-remagnetization - configured to uniquely flip the polarity of single-domain ferromagnets - has dramatic effects on the behavior of many birds, honeybees, mole rats, turtles, and bats, to cite a growing list. Magnetite-containing cells in the vicinity of these neurons in fish are now the subject of intense study by our consortium. The existence of a specialized class of magnetite-containing magnetoreceptor cells in animal tissues is no longer controversial. In contrast, less success has been achieved in gaining experimental support across a range of taxa for the radical-pair hypothesis. Although this mechanism was proposed to explain an early observation that birds would not respond to complete inversion of the magnetic vector, many organisms (even some birds) do indeed respond to the field polarity. We also note that few, if any, of these critical experiments have been done using fully double-blind methods. This is joint work with: M. M. Walker (University of Auckland, New Zealand) and M. Winklhofer (LMU Munich, Germany). [Preview Abstract] |
Wednesday, March 23, 2011 3:06PM - 3:42PM |
T38.00002: Magnetic compasses in biological systems: Does quantum physics play a role? Invited Speaker: One hypothesis of the process underlying the magnetic compass of animals surmises that the magnetic field is perceived by its effect on the coherent spin evolution within a non-equilibrium photochemical radical pair reaction. If this hypothesis were proven, it would be a dramatic demonstration of a quantum process with clear biological significance. We will review the physics of the radical pair mechanism and the current state of evidence supporting it. Experimentally, we will focus on the use radio-frequency magnetic fields to affect a radical-pair based mechanism in birds and discuss the approach and its limitations. Theoretically, we will focus on the question of how one should design a radical pair to be optimally sensitive to the direction of a weak magnetic field. Regardless of whether or not a radical pair mechanism is indeed used by birds or other animals, optimal design features could be used to manufacture biologically inspired, but man-made magnetic compass systems. [Preview Abstract] |
Wednesday, March 23, 2011 3:42PM - 3:54PM |
T38.00003: Quantum Control and Entanglement in a Chemical Compass Gian Giacomo Guerreschi, Jianming Cai, Hans J. Briegel The radical-pair mechanism is one of the two main hypotheses to explain the navigability of animals in weak magnetic fields, enabling, e.g., birds to see Earth's magnetic field. It also plays an essential role in spin chemistry. Here, we show how quantum control can be used to either enhance or reduce the performance of such a chemical compass, providing a new route to further study the radical-pair mechanism and its applications. We study the role of radical-pair entanglement in this mechanism, and demonstrate its intriguing connections with the magnetic-field sensitivity of the compass. Beyond their immediate application to the radical-pair mechanism, these results also demonstrate how state-of-the-art quantum technologies could potentially be used to probe and control biological functions. [Preview Abstract] |
Wednesday, March 23, 2011 3:54PM - 4:06PM |
T38.00004: A Biochemical Double Slit Iannis Kominis Radical-ion-pair reactions, fundamental in photosynthesis and at the basis of the avian magnetic compass mechanism, have been recently shown to offer a rich playground for applying methods and concepts from quantum measurement/quantum information science. We will demonstrate that radical-ion-pair reactions are almost the exact analog of the optical double slit experiment, i.e. Nature has already engineered biochemical reactions performing the act of quantum interference. We will further elaborate on the non-trivial quantum effects pertaining in these reactions and the recent debate on their fundamental theoretical description that these effects have sparked. [Preview Abstract] |
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